Sphygmomanometer utilizing optically detected arterial pulsation displacement

ABSTRACT

The invention relates to a sphygmomanometer capable of highly accurately judging the maximum blood pressure and minimum blood pressure, which has a cuff 10 which is attached to an appointed portion of a patient and presses the artery by supplying air therein; an optical range sensor 12 which is located opposite said cuff 10 and is able to detect the pulsation displacement of said artery; a digital processing section 14 which is able to judge the maximum and minimum blood pressure of said patient on the basis of photoelectric volumetric pulse wave signals sent out by said optical range sensor 12; and a display section 38 which is able to display the maximum and minimum blood pressure values judged by said digital data processing section 14. When increasing the pressure of the cuff 10 at a constant speed, said digital data processing section 14 is able to judge as the maximum blood pressure the point of disappearance of a photoelectric volumetric pulse wave signal and to judge as the minimum blood pressure the point of appearance of a flat section on the photoelectric volumetric pulse wave signal or its vicinity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sphygmomanometer, and in particularrelates to a closed type sphygmomanometer.

2. Description of the Related Art

A closed type electronic sphygmomanometer in which a cuff pressing theartery is wound on the upper arm of a patient is already known. For atonometry hemadynamometry method with this kind of sphygmomanometer,although there are an oscillometric process, a Korotoff's sound method,an impedance method, etc., the oscillometric process has been mainlyutilized in clinical applications. A sphygmomanometer in which atonometry hemadynamometry method utilizing such an oscillometric processis employed is disclosed by, for example, Japanese patent PublicationNo. 28637 of 1994.

A sphygmomanometer disclosed in the above publication is basicallycomposed of a cuff which is attached to the upper arm of a patient andpresses the artery by supplying air therein, a measuring section whichis able to detect the superposed pressure of the drop pressure and pulsepressure which change in said cuff and convert the same into digitalsignals, a digital data processing section which is able to obtain themaximum and minimum blood pressure values of a patient by using the cuffpressure detection signals outputted by said measuring section as inputdata, and a display section which is able to display the maximum andminimum blood pressure values calculated by said digital data processingsection.

With a sphygmomanometer constructed as described above, the maximum andminimum blood pressure values are judged by the digital data processingsection on the basis of fluctuations of the pulse pressure vibrationsand pulse wave amplitude while causing the pressure in the cuff to dropat a constant rate. However, there were the following shortcomings inthis tonometry hemadynamometry method with such an oscillometricprocess.

That is, in the tonometry hemadynamometry method, as has beenrepresented by an in-artery catheter method, the method for measuringthe pressure applied to a blood vessel wall by determining one point ofthe artery of a patient is ideal. However, with the tonometryhemadynamometry method by the abovementioned oscillometric method, sincethe pressure fluctuations in the cuff wound on the upper arm of apatient is detected and is used for measuring the blood pressure, apulse pressure appears even in the in-cuff pressure which is higher thanthe maximum blood pressure or it is not clear to judge the minimum bloodpressure.

With the tonometry hemadynamometry method with a conventionaloscillometric process, this results from detecting the mean pulsation ofthe artery spreading in the range of the cuff, and the pulsation is suchthat the artery wall displacement of the brachial artery resulting fromthe heartbeat is propagated as displacements of the skin surface andfurther the displacement of the skin surface causes the air capacity inthe cuff to be changed, wherein this capacity change is detected as apressure change in the cuff. Resultantly, the displacement quantity ofthe artery wall is converted to the pressure fluctuation in the cuff.

However, with such a method, since the displacement quantity of theartery wall is measured via air in the cuff, it is not possible tofaithfully obtain the artery wall displacement with only the pulsepressure wave obtained from inside the cuff because of receivinginfluences outside the body such as compression characteristics of air,damping characteristics thereof, etc.

This also means that although constituents of Korotoff's sounds whichhave higher frequency constituents than the pulse pressure waves aresuperposed with the pulse waveforms in a cuff pressure dropping processfrom the maximum blood pressure to the minimum blood pressure in theblood pressure measurement and must appear, fluctuations of higherfrequency constituents such as Korotoff's sounds are not able to bepropagated since air is used as a propagation medium in the in-cuffpulse pressure waveform in the oscillometric process, and resultantly itseems that such constituents do not appear.

That is, in a tonometry hemadynamometry method with a conventionaloscillometric process, since a cuff is wound onto a long length of thebrachial artery which is the portion to be measured of a patient and thepulse pressure vibrations are detected as pressure fluctuations in thecuff pressure, the artery pressure of the artery wall at one point whichis ideal in the tonometry hemadynamometry method is not accuratelyreflected. Accordingly, a pulse pressure wave occurs in the cuffpressure which is more than the maximum blood pressure, and since thepulse pressure wave is propagated by using air as a medium, thefrequency propagation is adversely influenced by the compressioncharacteristics and damping characteristics of air, and a shortcoming iscaused, whereby Korotoff's sound propagation is hindered.

SUMMARY OF THE INVENTION

The present invention was developed in view of solving theseshortcomings, and it is therefore an object of the invention to providea sphygmomanometer which is able to accurately measure the bloodpressure by directly measuring a local artery wall displacement.Disclosure of the invention

In order to solve the object, the invention is characterized in having acuff which is attached to an appointed portion of a patient and pressesthe artery by supplying air therein, an optical range sensor which islocated opposite said cuff and is able to detect the pulsationdisplacement of said artery, a digital processing section which is ableto judge the maximum and minimum blood pressure of said patient on thebasis of photoelectric volumetric pulse wave signals sent out by saidoptical range sensor, and a display section which is able to display themaximum and minimum blood pressure values judged by said digital dataprocessing section.

Said optical range sensor may be composed of a reflection plate providedinside an air bag of said cuff and light receiving and light emittingdiodes which are provided outside said air bag.

Furthermore, said optical range sensor has a pair of light receiving andlight emitting diodes, one of which may be provided inside said air bagof the cuff and the other of which may be provided outside the air bagthereof.

Said digital data processing section is able to judge as the maximumblood pressure the point of disappearance or appearance of saidphotoelectric volumetric pulse wave signals when raising or lowering thepressure in said cuff at a constant speed, and is able to judge as theminimum blood pressure the point of radical reduction of saidphotoelectric volumetric pulse wave signals or its vicinity.

When raising or lowering the pressure in the cuff at a constant speed,the digital data processing section is able to judge as the maximumblood pressure the point of appearance or disappearance of saidphotoelectric volumetric pulse wave signals and is able to judge as theminimum blood pressure the point of Korotoff's sound constituents fromsaid photoelectric volumetric pulse wave signals or its vicinity.

Furthermore, when raising or lowering the pressure in the cuff at aconstant speed, the digital data processing section is able to judge asthe maximum blood pressure the point of appearance or disappearance ofsaid photoelectric volumetric pulse wave signals and is able to judge asthe minimum blood pressure the point of appearance of a flat section insaid photoelectric volumetric pulse wave signals or its vicinity.

A sphygmomanometer constructed as described above has an optical rangesensor which is secured opposite the cuff and is able to detect thepulsation displacement of said artery. On the basis of photoelectricvolumetric pulse wave signals outputted from said optical range sensor,since the digital data processing section judges the maximum bloodpressure and minimum blood pressure of a patient, the displacementquantity of a local artery wall is able to be directly measured, and itis possible to obtain the maximum blood pressure value and minimum bloodpressure value on the basis of this displacement quantity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the total construction showing a preferredembodiment of a sphygmomanometer according to the invention, FIG. 2 is adeveloped view of a cuff for a sphygmomanometer of FIG. 1 and across-sectional view of major parts thereof, FIG. 3 is a flow chartshowing one example of processing procedures when measuring the bloodpressure by a sphygmomanometer shown in FIG. 1, FIG. 4 is a pulse wavediagram showing one example of pulse waves detected by asphygmomanometer shown in FIG. 1, FIG. 5 is a pulse wave diagram showinganother example when measuring the minimum blood pressure by asphygmomanometer shown in FIG. 1, FIG. 6 is a pulse wave diagram showingstill another example when measuring the minimum blood pressure by asphygmomanometer shown in FIG. 1, and FIG. 7 is a pulse wave diagramshowing further another example when measuring the minimum bloodpressure by a sphygmomanometer shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the invention are described with reference tothe accompanying drawings. FIG. 1 through FIG. 4 show a preferredembodiment of a sphygmomanometer according to the invention. Asphygmomanometer shown in these drawings has a cuff 10, an optical rangesensor 12, and a digital data processing section 14. Said cuff 10 isapplied to an appointed part of a patient, and concretely is applied tothe upper arm 16, the detail of which is shown in FIG. 2.

Said cuff 10 shown in the drawing is made of thin synthetic resin and isformed to be arcuate. Said cuff 10 consists of a bendable and deformablehard curved plate 10a, an outer cloth 10b which surrounds the outercircumference of said curved plate 10a, an inner cloth 10c sewed to saidouter cloth 10a so that the same is able to surround the innercircumference of said curved plate 10a, an air bag 10d provided insidethe inner cloth 10c, and an engaging fastener 1e sewed to the outercircumference of said outer cloth 10b, which is engageable with the endportion of the inner cloth 10c.

Said air bag 10d is a transparent sealed bag member 10g made ofsynthetic resin sheet, which has reinforcing fibers 10f incorporatedtherein in a latticed state. Said reinforcing fibers 10f are integrallyincorporated so as to prevent the same from being elongated whencompressing air therein and the artery is in pulsation. When air issupplied into the bag member 10g via a tube 18 described later and saidair bag is inflated therewith, the bag member 10g is able to be inflatedin proportion to the supply quantity of air.

An air supplying tube 18 is caused to communicate with and is connectedwith the inside of the bag member 10g. A pressure sensor 20 and asolenoid control valve 22 are connected to the outer end of said tube18. And a pump 24 which sends out air is connected to the solenoidcontrol valve 22, whereby the solenoid control valve 22 and pump 24 arecontrolled by a pump control section 26.

Detection signals of the pressure sensor 20 are inputted into thedigital data processing section 14 via a band pass filter 28 and an A/Dconverter 30. Control signals are sent out from the digital dataprocessing section 14 to the pump control section 26 on the basis of thedetection signals of the pressure sensor 20. The optical range sensor 12is composed of a photocoupler 12a fixed at the outer surface of theouter section of the bag member 10g and a reflection plate 12b fixed onthe outer surface of the inner section of the bag member 10g so that thesame is opposite this photocoupler 12a.

The photocoupler 12a is such that a light emitting diode and aphototransistor are integrally combined with each other, and the same isset so that light emitted from the light emitting diode is reflected bythe reflection plate 12b and is made incident into the phototransistor.The output level of the phototransistor may differ according to thedistance between the photocoupler 12a and the reflection plate 12b,whereby output signals corresponding to the displacement of the arteryare sent out.

The light emitting diode of the photocoupler 12a is controlled to beturned on and off by a light emission control section 32 connected tothe digital data processing section 14. The digital data processingsection 14 is connected to the phototransistor of the photocoupler 12avia the band pass filter 34 and A/D converter 36, whereby the detectionsignals of the phototransistor are digitalized and inputted into theprocessing section 14.

Furthermore, with this preferred embodiment, since the bag member 10g isformed with a transparent synthetic resin sheet, the photocoupler 12aand reflection plate 12b are disposed at the outside thereof. However,in a case where the bag member 10g is formed with a non-transparentsynthetic resin sheet, the photocoupler 12a and reflection plate 12b aredisposed at the inside thereof.

With a sphygmomanometer according to the invention, the optional rangesensor 12 may be not only a combination of a photocoupler 12a and areflection plate 12b but also a combination of a light emitting diodeand a photocoupler. In this case, they may be disposed so that they areopposite the inside or outside of the bag member 10g.

The digital data processing section 14 is composed of a so-calledmicrocomputer, which includes a CPU and memory, And a display section 38which is able to display the maximum blood pressure and minimum bloodpressure is connected to this digital data processing section 14 via aninterface. In FIG. 3 is shown one example of processing procedures inthe blood pressure measurement which is carried out in this digital dataprocessing section 14.

When measuring the blood pressure, a cuff 10 is attached to the upperarm 16 of a patient, so that a reflection plate 12b is positioned on theartery of the upper arm 16, and cloths 10b, 10c are fixed by applyingthe same onto the engaging fastener 10e.

Furthermore, in this case, in order to securely position the reflectionplate 12b on the artery of the upper arm 16 of a patient, for example,as shown by hypothetical lines in FIG. 2, it is preferable that aplurality of optical range sensors 12 are disposed along thecircumferential direction. With such a construction, a reflection plate12b of any one of the sensors 12 is able to be positioned on the artery.In a case where a plurality of optical range sensors 12 are used, onewhich is outputting the largest output signals may be selected bycomparing the output values of the respective sensors 12.

Upon a completion of attaching the cuff 10, since the preparation ofmeasuring the blood pressure is then completed, the control procedure ofthe digital data processing section 14 is commenced, wherein firstly theinitial setting is carried out in step s1. This initial setting includesthe upper limit value of pressure given to the cuff 10 and the limit ofthe measuring time. After this initial setting is completed, acalibration of the pressure sensor 20 is performed in step s2, and anoutput signal is sent to the solenoid control section 22 in step s3 inorder to open the solenoid control valve 22.

Next, in step s4, the solenoid control valve 22 is controlled on thebasis of detection signals of the pressure sensor 20, wherein a constantspeed compression control which increases the pressure inside the airbag 10d of the cuff 10 at a constant speed is performed.

At this time, with a cuff 10 according to this preferred embodiment,since reinforcing fibers 10f are incorporated in a bag member 10g of theair bag 10d in a latticed state and a hard curved plate 10a intervenesat the outer circumferential side of the bag member 10d, the elongationand contraction of the bag member 10d are regulated, and at the sametime the expansion thereof outward of the bag member 10d is regulated bythe curved plate 10a, whereby the optical range sensors 12 are able tobe prevented from being displaced. Resultantly, it will be possible toexert pressure upon the artery with the outside position of the bagmember 10d kept constant.

Continuously, in step s5, flag i which expresses the number of arterywaves is set to zero (0), and at the same time the blood pressurejudgement flag F_(P) is also set to zero (0), whereby output signals ofan optical range sensor 12 are taken in. In step s6, it is judgedwhether or not the photoelectric volumetric pulse wave signals aredetected.

The photoelectric volumetric pulse wave signals judged herein are thoseshown in FIG. 4 and are those in which the part corresponding to theexpansion of the air bag 10d which is compressed at a constant speed iseliminated from the output signals of the optical range sensor 12, andparts corresponding to the pulsation per pulse are individuallyextracted and stored into memory.

In step s6, in a case where no photoelectric volumetric pulse wavesignal is detected, the process advances to step s7, wherein in a casewhere it is judged that the flag i is not larger than 1, the process iscaused to return to step s6. In this case, if it is judged in the firstprocess in step s6 that no volumetric pulse wave is detected, since theflag is set to zero (0) in step s5, the process is returned to step s6without fail.

Accordingly, it is judged in step s6 that a photoelectric volumetricpulse wave signal has been detected, it is judged in step s8 whether ornot a flat section exists in the photoelectric volumetric pulse wavesignals equivalent to one pulse detected in step s8. If no flat sectionexists, the process returns to step s6, wherein the process similarthereto is repeated. On the other hand, if it is judged that a flatsection exists in the photoelectric volumetric pulse wave signals, 1 isadded to the flag i in step s9, whereby this is regarded as a new flag iand the process advances to step s10.

In step s10, it is judged whether or not the flag i is 1. If it is 1,the minimum blood pressure is judged in step s11. The process returns tostep s6 in a case where the flag is not 1 in step s10 and when thejudgement of the minimum blood pressure is finished in step s11.

The process till the above judgement of the minimum blood pressure ismore concretely described below. For example, herein it is assumed thatthe photoelectric volumetric pulse wave signals P1, P2, P3, . . . Pn perpulse are extracted in a state shown in FIG. 4. It is judged in step s8whether or not any flat section exists in the respective photoelectricvolumetric pulse wave signals P1, P2, P3, . . . Pn detected in step s6.

Herein, in the process of increasing pressure in the air bag 10d at aconstant speed, in a case where the pressure in the air bag 10d is lowerthan the minimum blood pressure of a patient, the photoelectricvolumetric pulse wave signals pulsate without being influenced by thepressure of the air bag 10d (Photoelectric volumetric pulse wave signalsP1 to P6 in FIG. 4).

However, if the pressure in the air bag 10d becomes larger than theminimum blood pressure of a patient, a flat section s having no pressurefluctuation in the photoelectric volumetric pulse wave signals when theartery pressure is smaller than the pressure in the air bag 10d.Accordingly, this preferred embodiment is constructed so that aphotoelectric volumetric pulse wave signal at which a flat section soccurs for the first time in steps s8 to s10 is detected, and theminimum blood pressure is judged when this photoelectric volumetricpulse wave signal P7 is detected.

In the judgement of the minimum blood pressure in step s11, for example,the pressure in the air bag 10d at the moment when the photoelectricvolumetric pulse wave signal p7 at which a flat section s occurs for thefirst time is extracted may be made the minimum blood pressure value, orthe pressure in the air bag 10d at the moment when the photoelectricvolumetric pulse wave signal P6 immediately before the photoelectricvolumetric pulse wave signal p7 at which a flat section s occurs for thefirst time is extracted may be made the minimum blood pressure value, orthe mean value of the pressure in the air bag 10d at the moment when thephotoelectric volumetric pulse wave signal P7 and the photoelectricvolumetric pulse wave signal P6 are extracted may be made the minimumblood pressure value.

Furthermore, in the judgement of the minimum blood pressure in thiscase, as shown in FIG. 4, since a high speed displacement portion Kequivalent to Korotoff's sounds appears in the photoelectric volumetricpulse wave signals if the pressure in the air bag 10d becomes largerthan the minimum blood pressure of a patient, the photoelectricvolumetric pulse wave signal where this high speed displacement portionK occurs for the first time is detected in step s8, and the minimumblood pressure value may be obtained by the method already described instep s11. Furthermore, similarly, it is possible to obtain the minimumblood pressure value by detecting both the flat sections and the highspeed displacement portion K.

As described above, the minimum blood pressure is judged. Even though aflat section s exists in the photoelectric volumetric pulse wave signalafter the value is specified, it is not judged in step s10 that the flagi is 1. Therefore, the processing procedures in step s6 to step s10 arecarried out one after another. And if it is judged in step s6 that nophotoelectric volumetric pulse wave signal is detected, step s7 isexecuted again.

In the judgement in step s7 at this time, since the processing procedurefrom step s6 to step s1 is repeated several times, the flag i becomeslarger than 1 without fail. Therefore, step s12 is consecutivelyexecuted, wherein the maximum blood pressure is judged.

That is, with a sphygmomanometer according to this preferred embodiment,if the pressure inside the air bag 10d becomes larger than the maximumblood pressure when increasing the same at a constant speed, the arterypulsation is suppressed by the pressure, whereby no displacement occursin an optical range sensor 12. Taking note of this point, the point whenno photoelectric volumetric pulse wave signal will be detected is judgedas the maximum blood pressure of a patient.

When the maximum blood pressure is judged in step s12 and the valuethereof is obtained, the result of measurement is displayed on thedisplay section 38 in step s13. Consecutively, in step s14, after thepump 24 is caused to stop, the solenoid control valve 22 is made open tothe atmosphere in step s15 to cause the air inside the air bag 10d to berapidly exhausted. Here, the process ends.

On the other hand, in addition to the above procedures, as a constantspeed compression of the air bag 10d is commenced in step s4, it isalways judged in step s18 whether or not the pressure inside the air bag10d is larger than the initially set upper limit value. Furthermore,simultaneously with the above judgement, it is judged in step s19whether or not the measurement time is over. If it is judged that eitherof them exceeds the respective limits, the meaning thereof is displayedon the display section 38 in step s20, whereby the process is shifted tostep s14, and the measurement is interrupted.

Since a sphygmomanometer constructed as described above has an opticalrange sensor 12 which is disposed opposite the air bag 10d of the cuff10 and is able to detect the pulsation displacement of the artery canjudge the maximum blood pressure and minimum blood pressure of a patientwith its digital data processing section 14 on the basis ofphotoelectric volumetric pulse wave signals outputted from said opticalrange sensor 12, it is possible to directly measure the localdisplacement quantity of the artery wall and to obtain the maximum bloodpressure and minimum blood pressure on the basis of this displacementquantity, whereby it is possible to accurately measure the bloodpressure values.

FIG. 5 shows another example of judgement methods of the minimum bloodpressure, which can be employed for a sphygmomanometer according to theinvention. In the example shown in the same drawing, the photoelectricvolumetric pulse wave signals obtained by the optical range sensor 12are differentiated, and the minimum blood pressure can be judged withthis differentiated photoelectric volumetric pulse wave signals. In thesame drawing, the wave forms shown in the upper stage are photoelectricvolumetric pulse wave signals and those shown in the lower stage aretheir differentiated wave forms.

If the photoelectric volumetric pulse wave signals obtained by theoptical range sensor 12 are differentiated, the parts which are changingat a high speed, that the parts corresponding to Korotoff's sounds K'are intensified, and as shown at the right end in FIG. 5, they appear asa great change. Therefore, in this example, the part where Korotoff'ssound appears for the first time, or the vicinity thereof is judged asthe minimum blood pressure. According to such a judgement of the minimumblood pressure, since it is possible to accurately recognize the partcorresponding to Korotoff's sounds K', it is possible to more accuratelyjudge the minimum blood pressure.

FIG. 6 and FIG. 7 show still another example of judgement methods of theminimum blood pressure, which can be employed for a sphygmomanometeraccording to the invention. In the example shown in FIG. 6, each peakvalue of the photoelectric volumetric pulse wave signals obtained by theoptical range sensor 12 is obtained, the part at which the fluctuationratio is largest in the comparison of the values before and after thepeak value thus obtained is specified, whereby the rising of thephotoelectric volumetric pulse wave signal being the peak value isjudged as the minimum blood pressure.

In the example shown in FIG. 7, the amplitude of photoelectricvolumetric pulse wave signals obtained by the optical range sensor 12 isobtained, and the part of the maximum amplitude is specified bycomparing the obtained amplitude, whereby the rising of thephotoelectric volumetric pulse wave signal having the maximum amplitudeis judged as the minimum blood pressure. Such a judgement method of theminimum blood pressure is also employed in a conventional oscillometricmethod. However, with a sphygmomanometer of the invention, since adisplacement quantity of a local artery wall is directly measured by anoptical range sensor 12 and the maximum blood pressure and minimum bloodpressure are obtained on the basis of this displacement quantity, it ispossible to further increase the judgement accuracy of the minimum bloodpressure.

Furthermore, in the above preferred embodiment, a case where the maximumblood pressure and minimum blood pressure are judged in the process ofincreasing the pressure of the air bag 10g of the cuff 10 at a constantspeed is shown. However, the invention is not limited to thisembodiment. The maximum blood pressure and minimum blood pressure may bejudged in the process of reducing the pressure thereof at a constantspeed, wherein for example, the point at which a photoelectricvolumetric pulse wave occurs may be judged as the maximum bloodpressure. Industrial feasibility

As described in the above preferred embodiment, with a sphygmomanometeraccording to the invention, since the displacement quantity of a localartery wall is directly measured by an optical range sensor and themaximum and minimum blood pressure values are obtained on the basis ofthis displacement quantity, the invention is suitable for a closed typesphygmomanometer which is able to accurately obtain the maximum andminimum pressure values.

What is claimed is:
 1. A sphygmomanometer comprising:an inflatable cuffwhich is attached to a selected portion of a patient for applyingpressure to an artery when inflated; an optical range sensor which islocated on opposite sides of said cuff for generating photoelectricvolumetric pulse wave signals correlating to the pulsation displacementof said cuff caused by said artery; a digital processing means fordetermining a maximum and minimum blood pressure of said patient solelyon the basis of said photoelectric volumetric pulse wave signalsgenerated by said optical range sensor; and a display section fordisplaying the maximum and minimum blood pressure values determined bysaid digital data processing section, wherein when raising or loweringan inflation pressure inside the cuff at a constant speed, said digitaldata processing section determines said maximum blood pressure bydetermining a point of disappearance or appearance of said photoelectricvolumetric pulse wave signals, and determines said minimum bloodpressure by determining a point at which said photoelectric volumetricpulse wave signals rapidly decrease.
 2. A sphygmomanometer as defined inclaim 1, wherein when raising or lowering the pressure inside the cuffat a constant speed, said digital data processing means determines apoint of disappearance or appearance of said photoelectric volumetricpulse wave signals as the maximum blood pressure, and determines a pointat which Korotoff's sound constituents appear from said photoelectricvolumetric pulse wave signals as the minimum blood pressure.
 3. Asphygmomanometer as set forth in claim 1 or 2, wherein when raising orlowering the pressure inside the cuff at a constant speed, said digitaldata processing determines a point of disappearance or appearance ofsaid photoelectric volumetric pulse wave signals as the maximum bloodpressure, and determines a point, at which a vicinity of a flat sectionappears with respect to said photoelectric volumetric pulse wave signalsas the minimum blood pressure.
 4. A sphygmomanometer as set forth inclaim 1, further including a plate for limiting the outer dimensions ofthe inflatable cuff.